To provide viable bridged (i.e., Layer 2) network services, it is desirable to be able to test the connectivity between nodes the in network. Two categories of testing functionality that are common in network management involve testing end-to-end connectivity between two nodes (often referred to as a “ping” test) and learning the path that traffic travels to get from one node to another (often referred to as a “traceroute” or “tracepath” test). Well-known “ping” and “traceroute” functionality has been developed for Layer 3 networks (e.g., IP-based networks). Although the ping and traceroute functions work well in IP-based networks, these functions are not exactly transferable to Layer 2 (L2) networks such as Ethernet networks. A solution for providing L2 ping functionality has been implemented and accepted by many L2 network equipment providers. The solution for providing L2 ping functionality involves designating a well-known EtherType (Etype) to indicate that an L2 frame is an operations, administration, and maintenance (OAM) frame. The OAM frame is sent to a target network node by setting the destination MAC address to the MAC address of the target network node. When the destination MAC address of the OAM frame matches the system MAC address of the receiving network node, the network node looks next at the Etype. If the Etype is set to the Etype that is designated for OAM frames, then the frame is pushed to an OAM task in the control plane of the network node, where the frame's specific function (e.g., L2 ping) is identified. Although there is general acceptance on how to test end-to-end connectivity (i.e., L2 ping), this approach has limitations when it comes to learning the path that an L2 frame has traversed to get from the source node to the target node. Specifically, an L2 ping frame is not pushed up to the OAM task until it reaches its target node and therefore there is no opportunity for the frame to collect path information at intermediate nodes.
In view of this, what is needed is a technique for obtaining path information related to a bridged network.